Extremal graph theory is a branch of combinatorial mathematics that studies the extremal properties of graphs. Specifically, it focuses on questions related to the maximal or minimal number of edges in a graph that satisfies certain properties or conditions. The primary goal is often to determine the extremal (that is, maximum or minimum) values for specific parameters of graphs (like the number of edges, number of vertices, etc.) that meet certain constraints, such as containing a particular subgraph or avoiding certain configurations.
Graph connectivity refers to a property of a graph that describes how interconnected its vertices (or nodes) are. In the context of graph theory, connectivity helps to determine whether it is possible to reach one vertex from another through a series of edges. The concept of graph connectivity can be classified into several types, primarily focusing on undirected and directed graphs.
Category theory is a branch of mathematics that focuses on the abstract study of mathematical structures and relationships between them. It provides a unifying framework to understand various mathematical concepts across different fields by focusing on the relationships (morphisms) between objects rather than the objects themselves. Here are some key concepts in category theory: 1. **Categories**: A category consists of objects and morphisms (arrows) that map between these objects. Each morphism has a source object and a target object.